This invention relates generally to a skid control system and more particularly to an improved skid control system which is particularly adapted to be utilized in conjunction with controlling the brakes of a two-wheeled vehicle.
The possible dangers involved in riding a motorcycle are varied and well known. One of the more critical areas of concern in the use of a motorcycle and an operation of the vehicle with which a great number of injuries are associated involves the use of the braking system wherein the front or rear wheel or both wheels lock up during the braking operation. The resultant lock-up of the front and/or rear wheel of the motorcycle causes a loss of control of the vehicle due to the fact that the rotation of the wheel is important in maintaining directional stability of the vehicle and also the skidding of the wheel additionally causes a loss of directional control. Accordingly, it is highly desirable to include a reliable skid control system with motorcycle vehicles to preclude injuries resulting from skidding wheels during the braking operation.
Skid control systems for motorcycle vehicles have been proposed in the past but have involved certain defects. For example, a vacuum-actuated system has been proposed which is not totally reliable in operation due to the fact that the engines associated with motorcycle vehicles do not produce enough vacuum to properly actuate the system. Further, with a two cycle engine, the vacuum utilized in actuating the skid control system is shared with the fuel system of the vehicle. As is known, vacuum systems require large units for vacuum storage and the large springs required for operation take up a great deal of room. Additionally, the prior art systems have been found to operate poorly when the vehicle is being stopped on wet surfaces. It is the alleviation of these problems which the system of the present invention has been evolved.
With the system of the present invention, the system is capable of operating at extremely low speeds due to the fact that the system is adapted to be utilized with a hydraulic modulator unit which will develop suitable pressures at idle speed. Such a modulator unit is disclosed in the copending application of Thomas M. Atkins, Ser. No. 391,463, filed Aug. 24, 1973. Further, the system incorporates a triple integration circuit at the input section thereof wherein the tachometer pulses from the wheel speed sensor are integrated three times to provide a highly reliable vehicle wheel speed signal at low speeds. The system also includes an extremely low speed cut-off circuit which renders the system inoperative at speeds below a certain amount where the wheel speed signal may be unreliable.
The system further includes several circuit monitoring systems which provide a means for shutting down the skid control system in the event of a failure of any part of the skid control system. For example, the system includes a short or open sensor detector, which circuit is utilized to sense the sensor input to determine if a short or open has occurred at the wheel speed sensor. If this condition exists, the power supply circuit is shut down to preclude further operation of the skid control system. Further, the fail-safe system checks to determine the length of time the skid control module is providing an output and also checks if no output is provided when the module should have an output. Under these conditions, the system is again shut down if the condition persists. Further, the system determines if an unwanted output is provided by the skid control module when no output is required. In this case, the system is again shut down by disabling the power supply.
Accordingly, it is one object of the present invention to provide an improved skid control system.
It is another object of the present invention to provide an improved skid control system for use in conjunction with two-wheeled vehicles such as motorcycles.
It is another object of the present invention to provide an improved highly reliable tachometer circuit for use in conjunction with motorcycle skid control systems to provide an input wheel speed signal to the skid control module.
It is still another object of the present invention to provide an improved fail-safe monitoring system for continuously checking the operation of the skid control circuit to provide fail-safe operation of the skid control system.
It is a further object of the present invention to provide an improved short or open detector for the wheel speed sensor circuit for use in conjunction with two-wheeled vehicle skid control systems.
It is still a further object of the present invention to provide a self-check circuit for a vehicle speed ramp generator circuit utilized in conjunction with two-wheeled vehicle skid control systems.
It is still another object of the present invention to provide an excessive output fail-safe circuit and a no output fail-safe circuit for use in conjunction with skid control systems associated with two-wheeled vehicles.
It is a further object of the present invention to provide an improved hysteresis and temperature compensation circuit for use in conjunction with two-wheeled skid control systems.
It is still a further object of the present invention to provide an improved fail-safe circuit for monitoring the module response output circuit to determine if an unwanted output is provided to the valve in a braking system.
It is still another object of the present invention to provide an improved fail-safe circuit for detecting faults in the driver, time delay and regulator systems incorporated in skid control systems for a two-wheeled vehicle.